class Animal:
    def content(self):
        print('它们都是动物')

class Horse(Animal):
    def content1(self):
        print('它是马')


class Donkey(Animal):

    def content2(self):
        print('它是驴')

class Mule(Horse, Donkey):
    def content3(self):
        print('它是骡子')

m = Mule()
m.content()
m.content1()
m.content2()
m.content3()

print(isinstance(m,Animal))
print(issubclass(Mule,Animal))
print(issubclass(Mule,Horse))
print(issubclass(Horse,Donkey))
